This link is a copy of my spreadsheet:https://docs.google.com/spreadsheet/ccc ... sp=sharing
That will take you to a read-only copy. If you're signed into a Google account, you can "Make a Copy" from the File menu & will be able to edit it. Even without a Google account, you can export a copy for Excel, however the =googlefinance() function isn't supported in Excel so you'd need to find another way to fill in share prices (or do it manually).
Under normal circumstances only the blue cells need to be edited. Everything else is automatically calculated. If you decide whether to rebalance based on how far off-balance you've drifted, you might consider tweaking the conditional formatting rules in column H to your desired values. I currently have white/yellow/orange/red based on how far from 100% of the desired percentage they are.